Melanoid pigments derived from catechol-like precursors are widely distributed in nature, and in particular mammalian melanin, arising from 3,4-dihydroxyphenylalanine (dopa), occurs in both normal and atypical pigment cells. The oxidative conversion of dopa to melanin has long been considered to proceed via a pathway (postulated by Raper in the late 1920's) involving transient and fugitive intermediates (dopaquinone, cyclodopa, dopachrome, and indole-5,6-quinone) which have not yet been adequately characterized. It appears, therefore, of considerable importance to apply modern fastsweep electroanalytical methods to a definitive characterization of these elusive intermediates and of the transformations, now hypothetically though rationally, relating them. We have recently reported that the oxidative cyclization of dopa to dopachrome is kinetically controlled by the intramolecular cyclization of dopaquinone to cyclodopa, and that dopaquinone is too short lived (half life ca. 15 milliseconds at 20 degrees) to be observed spectrophotometrically as claimed in recent literature. Furthermore, the formation of 5,6-dihydroxyindole was directly observed in the physiological pH range. We propose, therefore, to undertake a further detailed study of the oxido-reduction behavior of cyclodopa, 5,6-dihydroxyindole and a number of its congeners, including low molecular weight oligomers, largely via cyclic voltammetric and chronoamperometric techniques, selected to elucidate the kinetic-mechanistic behavior of the intermediates in this important biogenetic pathway.